In recent years, due to a demand for additional reduction in the size of electronic components and electronic devices, efforts have been made to research, develop techniques and put techniques into practical use for applying a ferroelectric thin film to electronic components or electronic devices formed by applying a dielectric body, such as capacitors and piezoelectric elements. Among ferroelectric thin films, a ferroelectric thin film having the (111) plane preferentially crystal-oriented has versatility, and has, particularly, a characteristic of a high insulating pressure resistance as well as a basic dielectric characteristic. Meanwhile, lead zirconate titanate (PZT) is a ferroelectric body having a perovskite structure and exhibiting excellent dielectric characteristics. When the PZT is used as a dielectric thin film material, it is possible to obtain excellent electronic components and electric devices.
Therefore, a technique for forming a PZT-based ferroelectric thin film for electronic components by applying chemical solution deposition (CSD), in which film-forming processes are low in cost, and a sol-gel liquid which produces a uniform film composition in a substrate is used, is put into practical use. Additionally, since the ferroelectric thin film having the (111) plane preferentially crystal-oriented is used in a variety of fields and environments due to its versatility, there is a demand for improvement for higher lifetime reliability.
Therefore, thus far, a method for improving the lifetime reliability by adding elements such as La and Nb to PZT has been proposed (for example, refer to Patent Documents 1 and 2). In addition, with attention on the film structure of a PZT-based ferroelectric thin film, a method for improving the lifetime reliability by employing a structure in which the microstructure of the PZT-based ferroelectric thin film is controlled is proposed (for example, refer to Patent Document 3).